update_flow_js_block · Nocobase MCP: Risk & Policy

WHAT IT DOES

What update_flow_js_block does on Nocobase

AI agents use update_flow_js_block to create or update resources in Nocobase — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Nocobase environment.

WHY IT NEEDS A POLICY

Why update_flow_js_block needs a policy

This is a Write operation because it modifies (updates) existing JavaScript block code. It is not Destructive because the change is reversible (can be updated again). It is not Execute because the tool itself doesn't run the code—it only stores/modifies the code definition.

From the tool's definition Tool description states 'Update the JavaScript code of a JSBlockModel' — this modifies code that executes in the NocoBase sandbox. The example shows ctx.render() which executes arbitrary JavaScript within a sandboxed environment.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

update_flow_js_block Rate-limited

update_flow_js_block stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "update_flow_js_block": {
      "limits": [
        {
          "counter": "update_flow_js_block_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Nocobase, so you can run agents against it safely.

FAQ

Questions about update_flow_js_block

What does the update_flow_js_block tool do? +

Update the JavaScript code of a JSBlockModel inside a flowPage. Code runs in NocoBase sandbox — use ctx.render(htmlString) to render output. Example: ctx.render(. It is categorised as a Write tool in the Nocobase MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on update_flow_js_block? +

Register the Nocobase MCP server in PolicyLayer and add a rule for update_flow_js_block: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Nocobase. Nothing to install.

What risk level is update_flow_js_block? +

update_flow_js_block is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit update_flow_js_block? +

Yes. Add a rate_limit block to the update_flow_js_block rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.

How do I block update_flow_js_block completely? +

Set action: deny in the PolicyLayer policy for update_flow_js_block. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.

What MCP server provides update_flow_js_block? +

update_flow_js_block is provided by the Nocobase MCP server (puguhsudarma/nocobase-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.